CyB is correct: Emmo dominated at the slams when the field was fairly weak because the world's best players were pros, and thus banned from slam competition.
He was no bum or slouch, but not a GOAT-contender either.
Head to heads versus some top players from the ITF website. Emerson beat Laver more than once and these results are not all the matches these players played.
Versus Rod Laver
1968 Buenos Aires FR Clay (O) R.EMERSON 9-7 6-4 6-4
1969 Australian Open 16 Grass (O) R.LAVER 2-6 4-6 6-3 7-9
1969 Miami QF R.LAVER 7-5 3-6 4-6
1969 U.S. Open QF Grass (O) R.LAVER 6-4 6-8 11-13 4-6
1970 WCT Las Vegas SF R.LAVER 3-6 6-3 2-6 6-3 3-6
1970 WCT St Louis SF R.LAVER 6-4 5-7 3-6
1970 WCT Fort Worth FR R.LAVER 3-6 5-7
1970 WCT Vancouver FR R.LAVER 2-6 1-6 2-6
1971 WCT Miami SF R.LAVER 6-2 3-6 5-7
1971 WCT Quebec QF R.LAVER 6-3 6-7 6-7
1971 WCT Fort Worth SF R.LAVER 1-6 4-6
1971 GP/WCT San Francisco 16 R.LAVER 7-6 4-6 0-6
1973 WCT Miami QF R.LAVER 6-1 3-6 6-7
1973 WCT Richmond FR R.LAVER 4-6 3-6
1973 WCT Toronto FR R.LAVER 3-6 4-6
1973 WCT Brussels SF R.LAVER 6-4 4-6 1-6
1973 WCT Finals QF R.LAVER 5-7 2-6 5-7
Rod LAVER (AUS) Leads Roy EMERSON (AUS) : 16 to 1 *
Versus Ken ROSEWALL (AUS)
Year Tournament Round Surface Winner Score
1969 Sydney QF Grass (O) K.ROSEWALL 16-18 6-3 1-6 2-6
1969 Los Angeles QF R.EMERSON 6-3 2-6 6-3
1969 Bristol SF Grass (O) K.ROSEWALL 5-7 4-6
1969 Cologne Cup SF R.EMERSON 5-7 9-7 6-2
1970 WCT Dallas SF R.EMERSON 8-6 8-6
1970 GP/WCT Louisville QF Clay (O) K.ROSEWALL 4-6 1-6
1971 Australian Open QF Grass (O) K.ROSEWALL 4-6 4-6 3-6
1971 WCT Vancouver SF K.ROSEWALL 4-6 1-6
1972 WCT Denver 16 R.EMERSON 7-6 6-7 6-4
Ken ROSEWALL (AUS) Leads Roy EMERSON (AUS) : 5 to 4 *
Versus Andres GIMENO (ESP)
Year Tournament Round Surface Winner Score
1968 Buenos Aires SF Clay (O) R.EMERSON 1-6 6-4 8-10 6-4 6-4
1969 Cologne Cup FR A.GIMENO 3-6 17-19
1970 Sydney QF A.GIMENO 3-6 6-3 6-4 2-6 3-6
1970 WCT Dallas FR A.GIMENO 2-6 3-6 2-6
1970 WCT Vancouver SF R.EMERSON 6-3 6-3
1971 WCT Chicago 16 A.GIMENO 6-1 3-6 6-7
1971 WCT Quebec 16 R.EMERSON 7-6 7-6
1971 Canadian Open 16 A.GIMENO 1-6 5-7
Andres GIMENO (ESP) Leads Roy EMERSON (AUS) : 5 to 3 *
Versus Pancho GONZALES (USA)
Year Tournament Round Surface Winner Score
1968 French Open QF Clay (O) P.GONZALES 5-7 3-6 6-3 6-4 4-6
1970 WCT Fort Worth QF R.EMERSON 7-9 6-1 6-1
Roy EMERSON (AUS) is tied with Pancho GONZALES (USA) : 1 to 1 *
Now Laver was two years younger than Emerson and I think Gimeno is one year younger but Rosewall and Gonzalez were respectively two and eight years older than Emerson.
I'm of the opinion that Gimeno, over the course of his career was a superior player to Emerson but his career was that of a third wheel often to Laver and Rosewall, despite the fact he may have been the third best player in the world in the mid to late 1960's. He defeated Laver and Rosewall a number of times in the same tournament to win titles.
I've also read that Gonzalez and Emerson played numerous times over the years and that Emerson rarely defeated Gonzalez. However the ITF website says it's tied.